Right now, Miller64's big competitor is Anheuser-Busch's Bud Select 55, and the market segment is doing quite well. It's an important shift for Miller64. Until now, the two have been going at it with the same value proposition, with each claiming to be the lightest beer on the market.

Now, Miller64 wants to be seen as more of a lifestyle brand. "Miller64 is the perfect light-beer choice for today's consumers who are always on-the-go but strive to balance their responsibilities and social life," touted Miller64 marketing manager Rita Patel in a press release.

Both companies are also experimenting with new products in their race for the segment.

Anheuser-Busch has high hopes for Bud Light Platinum — a low calorie beer with more alcohol — which it launched with a big marketing campaign (which included Super Bowl spots). MillerCoors tried out MGD 64 Lemonade last year, but it failed within seven months.